Rail wheel

ABSTRACT

A rail wheel with a wheel body and wheel brake discs connected thereto with fastening elements on both sides is designed in such a way that at least in the respective contact regions of the wheel brake discs a mechanically and thermally highly resilient intermediate layer is arranged on the wheel body

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation of U.S. patent applicationSer. No. 12/811,131, filed 29 Jun. 2010, which is a U.S. nationalizationunder 35 U.S.C. §371 of International Patent Application No.PCT/EP2008/010931, filed 19 Dec. 2008, which claims the benefit ofpriority to German Patent Application No. 10 2008 003 923.3, filed 11Jan. 2008. The disclosures set forth in the referenced applications areincorporated herein by reference in their entireties.

BACKGROUND

The invention relates to a rail wheel.

In the known rail wheels, the wheel brake disks connected to the wheelbody on both sides are fastened to the wheel body by a plurality offastening elements, primarily throughbolts, distributed over thecircumference.

In this case, the wheel brake disks bear with integrally formed coolingribs, centering and fastening eyes directly against the wheel body, tobe precise against a circumferential wheel web which connects a wheelhub to an outer race.

However, considerable operationally induced problems arise due to thedirect contact of the wheel brake disks with the wheel body.

For example, during a braking operation, as a result of the axialtemperature gradients which occur, considerable excessive rises in thesurface pressure occur radially on the outside of the wheel brake diskbetween the wheel web and the contact regions. (If the respective brakedisk were not bolted to the wheel body, it would assume the shape of aBelleville spring).

In addition, the annular wheel brake disks have the tendency to deformin an opposed plate-like manner due to internal tensile stresses in thefrictional surfaces, which stresses occur due to high thermal loading.

Excessive rises in the surface pressures in the radially inner contactregions then occur in the cold state.

Due to a thermally induced “breathing” of the wheel brake disk, i.e. aradial contraction and expansion at intervals, a “frictional sliding”occurs in the contact regions during every braking operation.

Due to the above-mentioned excessive rises in the surface pressures,especially at high braking powers, scoring occurs between the wheelbrake disks and the wheel body in the region of the contact regions orlocal plastic deformation occurs in the wheel web, and this may lead inthe long term to damage, such as the formation of cracks, in the wheel.

SUMMARY

The invention is based on the object of developing a rail wheel of thegeneric type in such a manner that an operationally inducedoverstressing is prevented with structurally very simple means and, as aresult, the service life as a whole is increased.

This object is achieved by a rail wheel as claimed.

Scoring phenomena and, therefore, wheel damage are avoided by arranginga mechanically and thermally highly loadable intermediate layer at leastin the respective contact region between the wheel brake disks and thewheel body.

The thermally induced radial deformations of the wheel brake disk, whichare referred to as “breathing” in the prior art and occur duringbraking, are now ineffective, since the intermediate layer acts as itwere as a sliding layer on which either the wheel brake diskcorrespondingly slides, when the intermediate layer is held on the wheelbody in a radially secured manner, or the intermediate layer togetherwith the connected wheel brake disk moves in a sliding manner thereonrelative to the wheel body.

The planar dimension of the intermediate layer is expediently the samesize or larger than the associated dimension of the contact region ofthe wheel brake disks, and therefore a low surface pressure iseffective.

The above-mentioned scoring phenomena or plastic deformations in thewheel web are, therefore, prevented, and therefore the formation ofcracks arising as a consequence thereof is also effectively avoided.

This, of course, results in a significant increase in the service lifeof the entire rail wheel and in a noticeable improvement in operationalreliability.

For this purpose, it is also expedient to produce the intermediate layerfrom a metal sheet, the hardness of which is significantly greater thanthe hardness or strength of the wheel web.

A metal sheet made of stainless steel with polished surfaces, which iscustomarily present in the form of rolled stock, is ideally suited forthis purpose, wherein the tensile strength of a metal sheet of this typeshould be >1000 N/mm² and the thickness approximately 1 mm. However, inprinciple, other metal sheet thicknesses are also usable.

According to at least one implementation, the intermediate layers eachconsist of circular ring portions which are lined up in a row next toone another in the circumferential direction.

In this case, circular ring portions of 30°, 60°, 120° or 180° areconceivable. In principle, of course, the intermediate layer may bedesigned as a single-part sheet metal ring. The circular ring portionsare fastened in the radial direction in a form-fitting or frictionallyengaged manner. The form-fitting connection can take place either at thewheel web or on the contact side of the wheel brake disk.

By contrast, a frictional connection is achieved by correspondingdistortion by means of the bolted connection through which the wheelbrake disks are fastened to the wheel web or to the wheel body.

Further implementation details of the invention are characterized in thedependent claims.

BRIEF DESCRIPTION OF THE FIGURES

Exemplary embodiments of the invention are described below withreference to the attached drawings, in which:

FIG. 1 shows a partial cutout of a rail wheel according to the inventionin a sectioned side view,

FIGS. 2 and 3 each show a further exemplary embodiment of the inventionin an enlarged partial cutout corresponding to FIG. 1,

FIG. 4 shows part of the rail wheel in a top view,

FIG. 5 shows a further exemplary embodiment of the invention in anenlarged partial cutout in a sectional side view.

DETAILED DESCRIPTION

FIG. 1 illustrates a partial region of a rail wheel, specifically of oneof the regions in which wheel brake disks 2 are connected on both sidesto a wheel body 1.

In this case, a wheel web 3 of the wheel body 1, which wheel web formstwo circumferential, radially extending contact surfaces, has a bore 14through which a bolt 6 is guided, with which the wheel brake disks 2 arefixedly connected to the wheel body 1.

Each bolt 6, of which a plurality is furthermore distributed at an equalangular spacing on a circumferential circle, is guided through afastening eye 5 in the respective wheel brake disk 2, the end side ofsaid eye likewise forming a contact region in relation to the wheel web3, such as cooling ribs 4 of the wheel brake disk.

An intermediate layer 7 assigned to each wheel brake disk 2 is arrangedbetween the contact regions of the fastening eye 5 and the cooling ribs4 and the wheel web 3, and therefore the wheel web 3 and the contactregions of the wheel brake disk 2 bear against said intermediate layer.

Said intermediate layers 7 are composed of a mechanically and thermallyhighly loadable material, e.g., of a hard-rolled metal sheet, thehardness or strength of which is greater than that of the wheel web 3.

As can be seen particularly clearly in FIG. 4, the intermediate layers 7consist of circular ring portions which are distributed uniformly overthe circumference, wherein the number of circular ring portions canvary. For example, for twelve bolts 6, the same number of circular ringportions is provided, said portions accordingly each enclosing an angleof 30°.

For radial securing purposes, the intermediate layers 7 may be held in aform-fitting manner, to which end, in the example shown in FIG. 1, thewheel web 3 has steps 8 in which the intermediate layers 7 are locatedin a manner substantially secured against displacement in the radialdirection.

The intermediate layers 7 have corresponding openings for the passage ofthe bolts 6.

In the example shown in FIG. 2 in which, as in FIGS. 3 and 5, anenlarged illustration in the contact region of the intermediate layers 7is reproduced; the radial securing takes place in both directions, i.e.,to the outside and to the inside, by means of a sleeve 9, which isinserted into the bore 14 and is held in an axially secured mannerthere. The sleeve 9 protrudes over the wheel web 3 on both sides atleast by the thickness of the intermediate layers 7.

The outside diameter of the sleeve 9 approximately corresponds to theclear diameter of a central recess in the intermediate layer 7 such thatthe latter can easily be attached and is held in a manner securedagainst lateral displacement.

In the variant embodiments according to FIGS. 1 and 2, the intermediatelayers 7 are, therefore, locked on the wheel web 3. By means of thevisible extensive contact of the intermediate layers 7 with the wheelweb 3, the outside radius of which is determined by the radial width ofthe cooling ribs 4 which virtually form outer contact regions, theproduction of significant temperature differences between the metalsheet and wheel web are avoided and therefore so too are thermallyinduced distortions of the intermediate metal sheets in relation to thewheel. The metal sheets do not slide on the wheel web.

By contrast, the wheel brake disk 2 which is supported on the respectiveintermediate layer slides in the radial direction on the intermediatelayer 7 in the event of a thermally induced changing shape such thatscoring or damage of the wheel web is prevented.

In the sense mentioned above, the intermediate layers 7 are also lockedon the wheel web 3 in the example shown in FIG. 5.

For this purpose, the intermediate layers 7 have flanges 13 in theregion of the bores 14 in the wheel web 3, the flanges being in the formof collars and projecting into the bore 14, and corresponding in theoutside diameter thereof approximately to the clear diameter of the bore14 such that radial securing in both directions is ensured.

FIG. 3 illustrates a further example of fixing the intermediate layers7.

Here, the wheel brake disk 2, in the contact regions thereof which facethe wheel web 3, has steps 10 in each of which one of the intermediatelayers 7 is located and secured radially.

During a temperature-induced expansion and contraction of the wheelbrake disks 2, in the radial direction, the respective intermediatelayer 7 moves at the same time by the same amount such that theintermediate layers 7 virtually slide on the wheel web 3.

As can be seen in FIG. 4, there is a further type of radial fixing ofthe intermediate layers 7 in that punched-out portions are made in saidintermediate layers in the region of overlap with sliding blocks 11,which are arranged between the wheel web 3 and the wheel brake disks 2,said punched-out portions corresponding in the basic contour dimensionsthereof to the sliding blocks 11, wherein the sliding blocks 11 passthrough the associated punched-out portions, thus resulting inform-fitting positional fixing on the wheel web 3.

Since temperature differences occur between the wheel brake disk 2 andthe intermediate layer 7 during each braking operation, the intermediatelayer 7 is designed in such a manner that differences in curvature donot result in any distortion.

The intermediate layer 7 is configured such that the intermediate layer7 is provided on the outer and inner borders with contact portions 12which bear against the associated edges of the steps 8, 10 (FIG. 4).

In principle, a single-part intermediate layer in the form of a ring iscapable of functioning. However, due to the large diameter of the wheelbrake disks 2 for rail wheels, it is substantially more cost effectiveto use circular ring portions, wherein the latter are punched or cut bylaser beam or water jet.

In the example shown in FIG. 4, 60° circular ring portions are selected,and each intermediate layer 7 is provided on the outer border with twocontact portions 12 and on the inner border with one contact portion 12which is located in the center while the two outer contact portions arearranged, with respect to the length, in the outer border regions, thusresulting in three-point contact by means of which, as mentioned,distortion in the event of differences in curvature is prevented.

LIST OF REFERENCE NUMBERS

-   1 Wheel body-   2 Wheel brake disk-   3 Wheel web-   4 Cooling rib-   5 Fastening eye-   6 Bolt-   7 Intermediate layer-   8 Step-   9 Sleeve-   10 Step-   11 Sliding block-   12 Contact portion-   13 Flange-   14 Bore

1-18. (canceled)
 19. A rail wheel comprising: a wheel body; and wheelbrake disks connected to the wheel body on both sides with fasteningelements, wherein a mechanically and thermally highly loadableintermediate layer is provided between the wheel body and the wheelbrake disks at at least respective contact regions of the wheel brakedisks, wherein the intermediate layer is composed of a sheet ofstainless steel having a polished surface and having a greater strengththan the wheel body or a wheel web, and wherein the intermediate layerslides relative to the respective wheel brake disk, and wherein theintermediate layer is located in steps of the wheel web.
 20. The railwheel of claim 19, wherein sleeves are held in the wheel web in boresfor the passage of fastening elements for securing the wheel brakedisks.
 21. The rail wheel of claim 20, wherein, the sleeves protrude onboth sides beyond the wheel web and passing through openings in theintermediate layer, the outside diameter of the sleeves approximatelycorresponding to the clear diameter of the openings in the intermediatelayer.
 22. The rail wheel of claim 19, wherein, in the region of overlapwith the bores, the intermediate layer has collar-shaped flanges whichproject into the bores, the outside diameter of the flangesapproximately corresponding to a clear diameter of the bores.
 23. Therail wheel of claim 19, wherein, if the intermediate layer is a circularring portion, the circular ring portion has a contact section on theouter circumference, forming a respective end region, and a centrallyarranged contact section on the inner circumference, wherein the contactsections bearing against boundaries of the steps.
 24. The rail wheel ofclaim 19, further comprising sliding blocks provided between the wheelbrake disks and a wheel web and, in the region of overlap with thesliding blocks, wherein the intermediate layers have punched-outportions in which the sliding blocks engage, the basic contourdimensions of the sliding blocks approximately corresponding to a basiccontour dimensions of the associated punched-out portions.